X O U or J heads on a 416?

A friends street/strip brkt car, runs in our NSS class
'71 Demon, 340/416, stock 2.02 J heads, .475/.494" hyd. cam don't know @.050, approx 9.5:1?, TR with 2 650DP's, small hdrs, according to weight /mph makes around 420fwhp. Leaving over 100hp on the table with TF 190's and a .620 s/roller which its getting next year along with the rise in comp from the heads.